3-4 week chick can’t stand and shaking

Hi everyone,
We got 17 babies on May 24th from McMurray hatchery. All were doing well. Then 2 days ago I found one laying on her side unable to get up. I have had her inside since then but she still can’t stand. Today she is also shaking. She is still eating but have had to give water to her by dropper as I haven’t seen her drink on her own. I have added rooster booster vitamin/electrolyte to the water. She’s eaten some hard boiled egg and some canned cat food along with her normal chick starter. They were vac for Marek and cocci. My dh is going to make a sling for her today. Can anyone please advise what may be happening and how to treat? All 16 other chicks are fine. This one that is ill is a Whiting true blue pullet.

Sorry, I just saw this thread. I would second the recommendation for some vitamin/electrolytes, such as Poultry Cell 1ml daily. There is a condition called avian encephalomyelitis (AE,) that can cause tremors and lying on their sides. It can strike chicks under one month of age. More commonly, there is coccidiosis, and even though chicks may be vaccinated, it can be possible for them to still get it. You could treat her with Corid, but that can undo the coccidiosis vaccine. You could get some droppings checked for coccidiosis and worms by a local vet—call around for one. Offer the chick water often held up to her beak. Give some soft chopped egg, and wet chick feed. The chick chair or sling may help.